Experts weigh in on festive season diet hack - before you even take the first bite

Taking a stroll after a heavy meal is a time-honoured tradition during the festive season. But what about heading out for a walk before you eat?

The debate over whether exercising on an empty stomach is truly beneficial or a fitness myth has raged for years. With the party season upon us, we are revisiting the topic to see if "fasted walking" is a smart strategy during the period when we most tend to overindulge.

To separate fact from fiction, fitness expert Daniel Galindo breaks down the benefits, risks and best strategies for walking on an empty stomach without compromising your health.

Science-backed benefits of walking on an empty stomach

According to Galindo, walking before breakfast offers perks backed by hard science. "Studies have shown that exercising while fasted promotes fat oxidation," he explains. "Because glycogen levels are low, the body is forced to tap into fat reserves as an energy source."

This mechanism is particularly useful for those looking to optimise fat burning - a handy tool when navigating the calorie-rich Christmas period.

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Experts from Madrid's Metropolitan Sport Club & Spa agree. "Despite the controversy, fasted walking has been shown to offer clear benefits, particularly regarding fat loss. However, balance is key; don't prolong the walk indefinitely without eating," they advise.

Light to moderate walks of 30-60 minutes are the sweet spot for boosting fat burning without completely draining your energy.

How fasted cardio affects insulin and metabolism

Walking on an empty stomach does more than just burn calories; it can also boost insulin sensitivity - a key marker for metabolic health - and improve the body's overall energy efficiency. It can also serve as a powerful complementary strategy for those practising intermittent fasting, amplifying the positive effects on hormonal regulation.

Experts from Metropolitan highlight two key pieces of research that support this approach:

• A pivotal study published in the Journal of Physiology concluded that exercising in a fasted state improves insulin sensitivity and promotes greater utilisation of fat for energy. This is significant for both weight loss and the prevention of metabolic diseases.
• Research published in 2015 further supported the idea that fasted exercise enhances fat oxidation and blood sugar regulation, contributing to greater metabolic efficiency.

Fat oxidation vs. calorie burn 

A fundamental question remains: does walking on an empty stomach actually help us lose weight faster?

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While it undeniably increases fat burning during the activity, Galindo offers a reality check: "The total calorie burn at the end of the day doesn't differ significantly from walking after eating."

Ultimately, long-term weight loss depends more on your overall calorie balance (total energy in vs. total energy out) than on how your body sources fuel during a 45-minute walk.

Optimal intensity and walking duration for maximum results

If you choose to walk fasted, intensity and duration are the keys to success.

"Light to moderate walks of 30 to 60 minutes are ideal for boosting fat burning without depleting energy stores," suggests Galindo. 

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Walking for around an hour can be effective for burning fat; however, longer, higher-intensity walks may be necessary to improve cardiovascular fitness and physical performance.

That said, high-intensity activities while fasting can be counterproductive. Without glycogen (carbs) for fuel, pushing too hard increases the risk of fatigue and muscle breakdown (catabolism). If your goal is to improve cardiovascular fitness, you are better off fuelling up beforehand.

What to eat after your fasted walk

Once you return from your walk, nutrition is paramount - especially during the festive season when it is easy to slip into unhealthy habits. "Consuming enough protein and healthy fats is essential to maintain performance and promote muscle recovery," recommends Galindo, who advises sticking to a balanced, nutrient-rich diet for the rest of the day.

Fasted vs. fed: Should you walk before or after eating?

The choice between walking on an empty stomach or after a meal depends entirely on your goals.

• Fasted walking "activates fat metabolism as the primary energy source," explains Galindo. It is best suited for light-to-moderate activity and those targeting metabolic flexibility.
• Fed (post-meal) walking "tends to use glucose from the recently consumed food," says the expert. This is excellent for reducing blood sugar spikes after heavy Christmas meals. Another positive: the energy from the meal allows for longer or more intense sessions without the risk of rapid fatigue.

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Potential risks and side effects of fasted cardio

While the benefits are tempting, fasted cardio isn't for everyone. "Exercising while fasted can increase the risk of hypoglycaemia (low blood sugar), especially in people not accustomed to the practice," warns Galindo. This can manifest as dizziness, weakness or fainting.

Another risk is muscle catabolism, which occurs when the body uses muscle protein reserves for energy. This is more likely during prolonged, high-intensity training and in people who aren't consuming adequate nutrients throughout the day.

You should avoid fasted walking if:

• You have diabetes or blood sugar control issues.
• You are pregnant.
• You have a low Body Mass Index (BMI) or a history of eating disorders.
• You frequently experience dizziness or fatigue.

"It's essential to consult a health professional before attempting fasted walking if you belong to any of these groups," stresses Galindo.

Debunking common myths about burning fat fasted

There are several persistent myths surrounding this practice that need clearing up:

• Myth #1: It burns more body fat overall. False. Galindo clarifies that "although it increases fat oxidation during the walk, it doesn't guarantee greater long-term fat loss if your overall calorie balance isn't managed."
• Myth #2: It eats away your muscle. False. Significant muscle loss (catabolism) generally only occurs with prolonged, intense training combined with poor nutrition. Light walking is safe.
• Myth #3: It is extremely dangerous. False. "For healthy, well-adapted individuals, fasted walking is safe and beneficial," assures Galindo.

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Expert tips for starting a fasted walking routine

If you decide to give the pre-breakfast stroll a try, follow Galindo's golden rules for safety:

• Start small: Begin with short walks of 20-30 minutes to let your body adapt.
• Watch the pace: Maintain a moderate intensity to avoid fatigue.
• Drink up: Hydrate before and after your walk.
• Listen to your body: If you feel dizzy or weak, stop immediately. In the future, try having a small snack beforehand.

And always consult a doctor before embarking on this new fitness routine if you have any medical condition or doubts about whether you can walk on an empty stomach without any risk to your health.

About the expert:

 Daniel Galindo is a Sports Science graduate and Regional Manager at Spain's Vivagym.